Originally Posted by Tim Sneath
It seems that some people think we got rid of this altogether, when in fact we just removed it from the default settings since most people won't need it any longer. The quick way to get at it is to use the Win+R shortcut key combination at any time - this is what I tend to use most of the time.
If you want to restore it permanently to your Start menu, here's what you do:
1. Right-click on the Start menu and choose Properties;
2. Select the Start Menu tab and click on the Customize... button;
3. Ensure the "Run command" option is checked.
Now the Start / Run command will be restored to its full glory. Of course, you can swap in and out a bunch of other choices (I like the Administrative Tools to be right there, but I don't much care for Pictures, Games and Music to be top-level items on my work machine.) Here's how I have my default menu configured - you'll see it's also docked to the left-hand side of the screen: